SIMULATION: Transactions of The Society for Modeling and Simulation International

Stockton, Chip G.

doi: 10.1177/003754979105700301pmid: N/A

Wildberger, A. Martin

doi: 10.1177/003754979105700302pmid: N/A

Fishwick, Paul

doi: 10.1177/003754979105700303pmid: N/A

This column focuses on a single topic within the field of computer simulation. All the material comes directly from the electronic news group (bulletin board) called Simulation Digest. The Digest can be obtained over INTERNET by accessing the news group 'comp.simulation' or by sending e-mail to: '[email protected]'

Rozenblit, Jerzy W.; Jankowski, Piotr L.

doi: 10.1177/003754979105700304pmid: N/A

This paper proposes a new approach to simula tion modeling of natural systems in the context of water quality modeling in streams affected by point source pollution. The approach has a potential for application to other domains of natural resource modeling. Its conceptual basis is knowledge-based simulation and systems analysis. In the approach presented in this paper, a stream or its section is viewed as a collection of components, i.e. stream segments. The structure of a stream is its segments and their couplings. For each stream segment, a single constituent model describing processes affecting the segment's water quality is defined. Models are coupled in a hierarchical manner. The hierarchi cal, modular model specification results in a stream model comprised of a finite number of sub-segment models. Fundamental theoretical concepts supporting such a specification are described. A prototype simulation modeling environment to support prediction of water quality in streams has been implemented and tested. The proposed approach differs from other natural systems modeling frameworks in that it offers a) modular model specification facilities, b) high degree of model reusability, and c) support for model selection and coupling.

Sharon, Ariel

doi: 10.1177/003754979105700305pmid: N/A

Sahotay, H.S.; Edwards, G.L.; Falkner, A.H.

doi: 10.1177/003754979105700306pmid: N/A

This paper reports the simulation of a practical system which is being investigated as part of a research program in pattern recognition. It is used to show that the system is feasible and to establish the conditions in which the system is stable. SIMAN is used for the simulation enabling the user to integrate the discrete and continuous parts of the model in one package. The problem being investigated is the tracking of contours of a 2 dimensional object using a beam of light. Z-transforms have been used to model the opto-electronic contouring system. The shape is simulated either by waveform generation or by manual input of numeric data for nonuniform shapes. The paper describes the derivation of the model and the programming behind the simulation together with successful results.

doi: 10.1177/003754979105700307pmid: N/A

Howe, R.M.

doi: 10.1177/003754979105700308pmid: N/A

This paper describes a variation of the conventional two-pass explicit Adams- Moulton predictor-corrector integration methods which is suitable for real-time simulation. In this new method the first pass through the state equations uses an Adams-Bash forth type of predictor algo rithm to campute an estimate of the state at the n+1/2 frame instead of the n+1 frame, as is customary. This estimate is then used to compute the derivative at the n+1/2 frame which, along with derivatives at the n, n-1, n-2, ... frames is used in the final corrector pass to calculate the state at the n+1 frame. Unlike conventional two-pass Adams- Moulton methods, these new versions are compatible with real-time inputs. The paper shows that they are also superior based on dynamic accuracy measures and stability measures. A three-pass predictor-corrector integration algorithm compatible with real- time inputs is also presented and shown to yield significantly more accurate results than 3rd-order RK (Runge-Kutta) integra tion.

Stockton, Chip G.

doi: 10.1177/003754979105700309pmid: N/A

doi: 10.1177/003754979105700310pmid: N/A